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-rw-r--r--Documentation/virtual/kvm/api.txt9
-rw-r--r--arch/x86/kvm/svm.c7
-rw-r--r--arch/x86/kvm/vmx.c6
-rw-r--r--arch/x86/kvm/x86.c3
-rw-r--r--arch/x86/kvm/x86.h36
-rw-r--r--include/uapi/linux/kvm.h1
6 files changed, 58 insertions, 4 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e60be91d8036..dc674c2b8b31 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4111,3 +4111,12 @@ reserved.
2: MIPS64 or microMIPS64 with access to all address segments.
Both registers and addresses are 64-bits wide.
It will be possible to run 64-bit or 32-bit guest code.
+
+8.8 KVM_CAP_X86_GUEST_MWAIT
+
+Architectures: x86
+
+This capability indicates that guest using memory monotoring instructions
+(MWAIT/MWAITX) to stop the virtual CPU will not cause a VM exit. As such time
+spent while virtual CPU is halted in this way will then be accounted for as
+guest running time on the host (as opposed to e.g. HLT).
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1b203abf76e1..c41f03e5090a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1198,10 +1198,13 @@ static void init_vmcb(struct vcpu_svm *svm)
set_intercept(svm, INTERCEPT_CLGI);
set_intercept(svm, INTERCEPT_SKINIT);
set_intercept(svm, INTERCEPT_WBINVD);
- set_intercept(svm, INTERCEPT_MONITOR);
- set_intercept(svm, INTERCEPT_MWAIT);
set_intercept(svm, INTERCEPT_XSETBV);
+ if (!kvm_mwait_in_guest()) {
+ set_intercept(svm, INTERCEPT_MONITOR);
+ set_intercept(svm, INTERCEPT_MWAIT);
+ }
+
control->iopm_base_pa = iopm_base;
control->msrpm_base_pa = __pa(svm->msrpm);
control->int_ctl = V_INTR_MASKING_MASK;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c1a12b94e1fd..a4ef63718101 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3527,11 +3527,13 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
CPU_BASED_USE_IO_BITMAPS |
CPU_BASED_MOV_DR_EXITING |
CPU_BASED_USE_TSC_OFFSETING |
- CPU_BASED_MWAIT_EXITING |
- CPU_BASED_MONITOR_EXITING |
CPU_BASED_INVLPG_EXITING |
CPU_BASED_RDPMC_EXITING;
+ if (!kvm_mwait_in_guest())
+ min |= CPU_BASED_MWAIT_EXITING |
+ CPU_BASED_MONITOR_EXITING;
+
opt = CPU_BASED_TPR_SHADOW |
CPU_BASED_USE_MSR_BITMAPS |
CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 49a69c0a0d50..2f9fe6bf7091 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2687,6 +2687,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ADJUST_CLOCK:
r = KVM_CLOCK_TSC_STABLE;
break;
+ case KVM_CAP_X86_GUEST_MWAIT:
+ r = kvm_mwait_in_guest();
+ break;
case KVM_CAP_X86_SMM:
/* SMBASE is usually relocated above 1M on modern chipsets,
* and SMM handlers might indeed rely on 4G segment limits,
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e8ff3e4ce38a..612067074905 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -1,6 +1,8 @@
#ifndef ARCH_X86_KVM_X86_H
#define ARCH_X86_KVM_X86_H
+#include <asm/processor.h>
+#include <asm/mwait.h>
#include <linux/kvm_host.h>
#include <asm/pvclock.h>
#include "kvm_cache_regs.h"
@@ -212,4 +214,38 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
__rem; \
})
+static inline bool kvm_mwait_in_guest(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+
+ if (!cpu_has(&boot_cpu_data, X86_FEATURE_MWAIT))
+ return false;
+
+ switch (boot_cpu_data.x86_vendor) {
+ case X86_VENDOR_AMD:
+ /* All AMD CPUs have a working MWAIT implementation */
+ return true;
+ case X86_VENDOR_INTEL:
+ /* Handle Intel below */
+ break;
+ default:
+ return false;
+ }
+
+ /*
+ * Intel CPUs without CPUID5_ECX_INTERRUPT_BREAK are problematic as
+ * they would allow guest to stop the CPU completely by disabling
+ * interrupts then invoking MWAIT.
+ */
+ if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+ return false;
+
+ cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+ return false;
+
+ return true;
+}
+
#endif
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 3c168b6fd74b..e43906b95d9f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -893,6 +893,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_S390_GS 140
#define KVM_CAP_S390_AIS 141
#define KVM_CAP_SPAPR_TCE_VFIO 142
+#define KVM_CAP_X86_GUEST_MWAIT 143
#ifdef KVM_CAP_IRQ_ROUTING